Twice as good as the original. Running time: 134 minutes. Rated PG-13 (sci-fi violence, sexuality, mild profanity). At the Empire, the Ziegfeld, the Union Square, others.

———

‘X2″ is as irresistible as movie-theater popcorn – a lavish, reasonably intelligent, well-acted sequel with kick-butt effects that outdoes its predecessor, 2000’s “X-Men,” in almost every department.

Bryan Singer is back in the director’s seat and most of the original cast returns for this whirlwind epic, which has the wheelchair-bound mentalist Dr. Xavier (Patrick Stewart) and his band of not-so-merry mutants teaming up with his arch-nemesis Magneto (Ian McKellen) to stop a bigoted military scientist (Brian Cox) bent on ethnically cleansing the mutant population.

That Singer has raised the ante is clear from the bravura opening sequence set in the White House.

Frightening newcomer Nightcrawler (Alan Cumming) – with blue skin, a tail and the ability to teleport himself through walls – defies the Secret Service and tries to assassinate the president.

Xavier rightly fears the attack will renew calls for a Mutant Registration Act – and worse.

What’s worse is the shadowy Stryker (Cox), who launches a SWAT team attack on the Westchester mansion where Xavier trains young mutants to be X-Men.

And even worse than that, Stryker knows about the device Xavier uses to keep track of all mutants on Earth – thanks to Magneto, who has fallen under the scientist’s control.

That is, until Magneto busts out of his glass prison – a truly spectacular sequence – with the help of Mystique (sexy Rebecca Romijn-Stamos), his blue-skinned, shape-shifting Gal Friday who can impersonate anyone.

With Xavier temporarily sidelined under Stryker’s control, it’s up to Magneto to lead the X-Men who escaped the SWAT attack in an assault on Stryker’s mountain fortress.

That’s where Wolverine (Hugh Jackman) meets up with Stryker’s mutant sidekick Yuriko (Kelly Hu), who shares Wolverine’s retractable claws, his ability to regenerate himself – and maybe a lot more.

Wolverine also has unresolved romantic issues with the telepathic Jean Grey (Famke Janssen) and her boyfriend Cyclops (James Marsden) – not that Rogue (Anna Paquin) has gotten over her infatuation with the hirsute Wolverine, despite her new boyfriend Iceman (Shawn Ashmore).

Besides the dependably evil Cox and Cumming’s scene-stealing Nightcrawler – who turns out to be a deeply devout former circus acrobat and not a bad guy – the other major addition this time around is Pyro, whose name is self-explanatory and is played by Aaron Stanford of “Tadpole.”

Her Oscar notwithstanding, Halle Berry, who returns as the weather-controlling Storm, doesn’t have a whole lot to do – though she sports a new hairdo.

“X2” includes an excellent, rousing score by the versatile John Ottman, who edited the overlong movie – though there is an interesting scene where a budding X-Man “comes out” to his family.

Like last summer’s “Minority Report,” “X2” is partly a cautionary tale about the government trampling civil liberties during an “emergency” – a theme that couldn’t be more timely.

But for all of its considerable assets, “X2” isn’t going to be of huge interest to anyone who doesn’t want to see a movie based on a comic book.